Characterizing anomalous transport in pulsed power systems by advancing kinetic theory and continuum kinetic simulations

Pulsed power inertial confinement fusion experiments at the Z facility study high energy density physics and rely on magnetically insulated transmission lines to deliver up to 26 MA of current to a Z-pinch load. Low-density plasmas that form on electrode surfaces of these transmission lines are subject to poorly-understood anomalous transport, which leads to parasitic currents and undermines predictive modeling of the load. Characterizing anomalous transport physics is theoretically and computationally challenging because kinetic theory is often intractable while accurate kinetic simulations are computationally costly. In effort to address these challenges, we have developed new theoretical and computational capabilities that capture nonlinear properties of low-beta kinetic-regime plasmas present in pulsed power systems. The effort has been facilitated by noise-free conservative fourth-order accurate Vlasov-Poisson simulations, which have recently been accelerated by leveraging graphics processing unit (GPU) hardware. The theoretical and computational analysis has shed light on gyromotion-modulated mass transport driven by Kelvin-Helmholtz instabilities and on momentum and energy transport driven by lower hybrid drift instabilities. The results have contradicted broadly-held notions about transport physics, especially concerning the degree to which gyromotion is important and the degree to which leading nonlinear theories can be believed.